1. Field of the Invention
This invention relates to polymers containing hydroxymaleimide repeat units, and, more particularly, to a process for making hydroxyamino-derivatized polymers of .alpha.-olefin-maleic anhydride, half-acid/half-ester or full acid copolymers, which find application in personal care products.
2. Description of the Prior Art
Maleic anhydride can be reacted with amines to form the corresponding maleamic acid derivative. Suitably, a maleic anhydride containing polymer is reacted in solution or suspension with an amine in inert or non-reactive solvents, such as acetone, heptane, benzene or dibutylether, to provide the desired maleamic derivative.
Unfortunately, various side reactions occur during such solution or suspension processes which adversely affect the quality of the final product, particularly its color and odor. In addition, the amine reactant can form a salt with the half-acid polymer instead of reacting with the anhydride, thereby reducing the yield of the desired amide reaction product.
The reaction of amines with anhydride polymers in an inert solvent also is difficult to control because of its rapid reaction rate and high reaction exotherm leading to the formation of a non-homogeneous reaction product.
Reactions of anhydride polymers with amines in inert solvents present other problems, too. For example, if the reaction is conducted as a slurry, e.g. reaction of p(methyl vinyl ether-maleic anhydride copolymer) with an amine in toluene, the consistency of the slurry may change as the amine reacts with the anhydride polymer. This change in consistency usually results in excessive swelling of the polymer during the reaction, which can make subsequent processing very difficult unless the slurry is sufficiently diluted with solvent. However dilution reduces polymer capacity.
Reaction of an anhydride polymer with an amine as a solution in an inert solvent such as acetone is advantageous but it may result in considerable gelling or precipitation of the reaction product or the formation of "fish eyes".
As described in said copending U.S. patent application, the reaction of maleic anhydride containing polymers with amines in a reactive solvent such as ethanol produces a homogeneous product in the form of a solution or stable collodial suspension which is easy to handle even at a high solids content. Such process provides a practical route to the synthesis of amine-derivatized polymers of maleic anhydride half-acid/ester or full acid in the form of its predetermined ratios of maleamic acid and maleimide repeat units.
However, this process is not as useful for the derivatization of polymers of maleic anhydride with bifunctional amine reactants such as hydroxyamines because both of their hydroxyl and amino functionalities can react at both ends of the molecule with the maleic anhydride moiety in inert or nonreactive solvents. These secondary reactions may produce crosslinked products, which are not particularly desirable for use in personal care and pharmaceutical compositions when a solvent soluble product is desired.
Accordingly, it is an object of this invention to provide water or alcohol soluble amine derivatized maleic anhydride containing polymers which include hydroxymaleimide repeat units in a predetermined amount, with maleamic acid repeat units and .alpha.-olefin-maleic anhydride-half acid/ester or full acid repeat units, and of a process for making such polymers having little color or odor and substantially no free amine.
A feature of the invention is the provision of such advantageous polymers by carrying out the derivatizing reaction in an aqueous or aqueous-alcoholic solution as a reactive solvent.
Another feature of the invention is the provision of suitable reaction temperatures and reaction times in the process which can predetermine the ratio of the maleic anhydride half-acid/ester, maleamic acid and maleimide repeat units in the derivatized polymer obtained.
Yet another feature herein is to provide a derivatizing reaction which can be carried forward substantially to completion with little or no unwanted side reactions.
Yet another feature is a derivatization reaction which does not require an esterification or acidification catalyst, and is conducted in a non-toxic solvent.
Among the other features of the invention is the provision of a terpolymer product having little color or odor and substantially no free amine.
These and other objects and features of the invention will be made apparent from the following detailed description of the invention.